Update README.md (postgres, elasticsearch, project setup)
Update README.md (postgres, elasticsearch, project setup)

- add technical requirements
- add more detailed postgres info
- add elasticsearch setup & check info
- improve formatting/markdown
- reorder and categorize sections
- remove duplicate info
- correct elasticsearch version install
- add prompt symbol to shell commands

rubymonsters/speakerinnen_liste,1000miles/speakerinnen_liste,1000miles/speakerinnen_liste,1000miles/speakerinnen_liste,rubymonsters/speakerinnen_liste,rubymonsters/speakerinnen_liste